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Another DIY Powerwall in Germany (15 kWh)
Hi there!

name's Alex Smile
Just finished my powerwall project, which I have started in the end of february.

All cells were harvested from used/bad e-bike batteries. Most of the time, about 2-3 cells in each pack were bad (high inner resistance or very bad capacity), the rest usually was just fine


I tested the cells using 5 Opus chargers in parallel.

In total, I've tested about 2300 cells, some were bad, some mechanically damaged. Some got hot during charge (some sanyo, but also some panasonic). Of course, I threw out all these bad cells. Still, I've ended up with 1960 good cells, the average cell capacity is 2100 mAh. My cell configuration is 14s140p.

The wiring of the cell  holders was straight forward. I used 1.6 mm copper wire for the bars and 0.2 mm tinned copper wire for fuses (double fuses + and -)

The Powerwall is hooked onto a PIP 5048MS (PF1). Charge end voltage is 4.09 V / cell and discharge end voltage is 3.3 V / cell. Power is coming from a 4.5 kWp solar array.

I'm not using a BMS. Each cell block has a little voltage readout and a passive balance board that kicks in at 4.1 V (2A current).

I have found a software, that automatically calculates the pack layout for the 1960 cells. This worked so well, that the voltage drift between the cells is minimal. Deepest discharge so far was 3.55 V and the difference between each pack was less than 0.02 V. I didn't expect that, but of course I'm happy Big Grin
Also when recharging, the balancer modules did not yet get active. All packs equally charge up and perfectly end up at 4.09 V without the need for balancing (yet).

I'll see how the pack behaves the next weeks / months.

best regards,
Wattsup, prudhvychoudary15, IronSky And 12 others like this post
Where did you get that passive balance board? Or did you build them yourself? In that case please share more details.
Hi Alex,

erstmal herzlich willkommen hier Smile !

Great work, nice shelf. Since you've more cells than I have in my powerwall, you'll push me down one position in the cell counter... Dodgy Big Grin .

Where exactly do you live?

I'm also interested in the passive balancers you're using. And I would like to check out the software you've found. I wrote it by myself, can be configured for packs size and number and serial rows, also with min. capacity, min. voltage and max. voltage drop between two meassures.

And maybe you wanna check out my project...

Have sun!

Cells tested: 6.721 (overall cap.: 13.587 Ah, average cap.: 2.021 mAh)
Cells in production: 3.500 (overall cap.: 7.350 Ah, average cap.: 2.100 mAh)
Powerwall setup: 7s500p, 1.050 Ah, 27 kWh
Project page
Live solar/powerwall values
Daily graph
Hallo Alex,
auch von mir herzlich Willkommen Smile

Super work you have done there. I also use batteries from e-bikes, but unfortunately I have not as many as you.

Sometimes you have also bad luck with the E-bike batteries and does not get 18650 cells. They are Li-poly or very different formats.

for example cells from Koga Akku :

The best experiences I have made with the batteries of Bosch and Gazelle. There were always 18650 in it.

Viel Glück noch mit deinem Projekt , vielleicht kann man sich ja mal helfen bei den Akkus.

Schöne grüsse aus NRW


Thank you for the nice welcome Smile
I'm located in the south of Germany near Munich.
The passive balancers are from they basically can be set at any voltage and as I don't want mine to fully charge up to 4.2 V, I have them set to 4.1 V.

Was trying to attach the software here, but it didn't accept the file format Huh . It's a simple java app and cell data can be imported from .txt

Check the screenshot how this looks like. I have a text file with cell number and cell capacity. Using the java app I have made the excel sheet which tells mit which cell goes into which cell block Smile

best regards,
Where did you manage to find the ebike batteries?
Wellcome, nice setup you have, I already tested your app, posted yesterday here, with credits to endless sphere forum, so now you can claim your merits.

Lot of stuff on that page, what is exactly your balancer?

Wow, it stinks when you can get a cordless drill cheaper than some wires:

Cordless screwdriver 3,6 Volt Bruder Mannesmann M17730 Special price : 17,85 €
Special charging cable for 1-6 Lipo BEC connector system 40,00 €

The cables look to be just XT connectors on the ends. Supply and demand, I suppose.

Welcome to the group, and nice layouts and construction Smile
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I'm using this balancer (with special 4.1 V bypass):

The cells are almost all from a local e-bike shop. I guess about 40 % Samsung, 30 % Panasonic, 25 % Sanyo, 5 % rest (LG, Lishen)

Hallo Alex,
auch von mir herzlich willkommen im Forum!

Very nice work you have done so far.
I'm very curios to see your progress without the balancer. Let's see the behaviour of the packs.

Alles Gute

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